Create a zoomable starfield
From the experience with my camera at home, zooming in on a starry sky from 28mm up to 400mm the stars definitely become bigger, too - there are still no observable details, but zooming in makes the &quot;blotches&quot; larger. And another thing, zoomed in you will see more stars than zoomed out, because the much smaller ones are magnified as well. Of course this is also depending on how fast your lens is, if it doesn't get enough light zooming in results in darker, less visible stars. But the size definitely changes.
So if you zoom in on an object that's further away instead of moving towards it, the relative position of the starry background doesn't change much, so you're right that you'd see fewer stars (of the bright ones you're seeing zoomed out, but more darker ones might appear).
To avoid having pixelated stars I'm not using an Environment Texture for this, I'm creating a fully procedural background with muktiple Voronoi Textures at different scales. Plugging the Distance output into a Color Ramp you get very small circles if you set the ramp's left slider to white, the right one to black and bring it very close to the left. I multiply the ramps' outputs with different values so that the larger stars are brighter than the smaller stars.
The best is to decide how large you make the different star sizes when zoomed in. If they become invisible when zoomed out, you might make them brighter by multiplying with a higher value or compromise by tweaking the size a little bit. Here is a typical setup I use:

Of course you can add even more Voronoi Textures with varying sizes or even colorize the stars with this. That's one of the reasons I'm using 4D instead of 3D in the voronoi settings. If I like to have different colored stars but at the same size, I duplicate the node and change the W value.